Keep around a lot of water, flowing, in warm weather

Usage examples of heatwave.

There's an instant of flicker across what remains of the saloon's front, almost like a heatwave, and for that one instant, anyone who had been looking would have seen the E-Z Stop behind the burning Lady Day like a ghost-building or a double exposure, the convenience store also half-demolished and also burning.

Atop a large, white boulder, twenty yards or so to the left of the two magicians, there was a shimmering disturbance in the air, somewhat like heatwaves rising from a red tile roof on a hot day.

Although it was scarcely midmorning, the sun was already a furnace, and shimmering heatwaves rippled the valley floor ahead, making the dusty, gray-green bushes seem to dance in the windless air.

His moods were a series of heatwaves inexorably rippling toward a storm, which broke when he drunkenly barged into my flat one night and accused me of trying to emasculate him.

This was worse than the flash heatwave that had led a whole warehouseful of Lancre Extra Strong to riot.

So far she had balked her utterly and completely, necessitating this stupid trip during what the weather forecasters were calling the worst heatwave to hit New England since 1974.